We are currently genotyping subjects with the Affymetrix 1 Million SNP chip technology. Phase 1 was designed to detect potential associations with young-onset T2DM, by genotyping 300 early-onset T2DM subjects (onset age<25 yrs) and 329 non-diabetic controls (age >45 yrs), and 271 additional subjects who were diabetic and non-diabetic siblings of the selected subjects. Associations for T2DM will be calculated using both a case/control analysis (N= 629) and a within-family analysis (482 siblings from 169 sibships), and SNPs that had the strongest association for the combined associations were prioritized. Phase 2 of the GWA was designed to detect associations with pre-diabetic traits (% body fat, insulin action as measured by the hyperinsulinemic euglycemic clamp technique, and the acute insulin response to an intravenous bolus of glucose). Six hundred non-diabetic subjects who had been metabolically phenotyped for these predictors of T2DM are genotyped using the 1 Million SNP chip. SNPs will be prioritized for detailed follow-up studies that are associated with both a pre-diabetic trait and early-onset T2DM in GWA Phase 1.